CIWS whats wrong with it?

Two problems. One is a range issue: RIM-116 can knock down inbounds at much greater range. Some of the large supersonic ASMs that get hit by Mk15 can theoretically have enough momentum that they will hit the ship regardless. Alternatively, if it explodes, it'll still be close enough to pepper the ship with fragments.

The other is ammunition. The Mk15 carries enough ammo for a good six or seven killing bursts before needing a reload. The RIM-116 launcher which is about the same size carries 21 missiles.

NTM

Interesting...checked USS ENTERPRISE's website and photos still have her with 3 CIWS mounts. Checked the Navy's website and they're still on all Carriers. I know some NIMITZ Class Carriers and WASP Class LHDs have CIWS, RAM mounts, and Sea Sparrow launchers.

My off the cuff, unsubstantiated reaction is that it may be repalced by Metal Storm which is a new type of gatling gun/CIWS system. Thought I heard something to that effect somewhere but not sure if it is true.

I'm no expert, but I think it's more of a move to the Rolling Airframe Missile system than it's really a knock on the Phalanx system. If I remember my reading, the RAM gives you better range on the intercept (farther from the ship is a very good thing) and more control, too. Can't really abort/remote detonate 20mm slugs once their fired, where with RAM you can. Just a guess on my part, maybe someone else knows more?

A quick Google search shows nothing negative through the first 5 pages of links.